1. Field of Invention
This invention relates to improvements in indirect evaporative cooling technology, and particularly to indirect/direct evaporative cooling devices used in conditioning air.
2. Description of Related Art
Two-stage evaporative coolers, also known as indirect/direct evaporative coolers (IDEC's), have enormous potential to provide indoor comfort and simultaneously reduce energy consumption by replacing traditional vapor compression air conditioning systems in dry to moderately dry climates. IDEC units can have more cooling capacity than traditional single stage (i.e., direct) evaporative coolers, and add less moisture to the conditioned space. IDEC units do not use a compressor and are therefore significantly more energy efficient than traditional air conditioning systems. IDEC's combination of energy efficiency, high cooling capacity, and relatively little moisture addition promises significant societal benefit by mitigating the environmental damage associated with conventional air conditioning systems. IDEC units are potentially very effective at reducing electricity use during summer afternoon hours, when most utilities face peak demand.
Modern indirect evaporative cooling is typically accomplished by passing air through a system of thin parallel heat exchange plates with alternating dry and wet passages. A first airstream is passed through the dry passages; simultaneously, a second airstream is passed through the parallel wet passages. Water is supplied to the surfaces of the heat exchange plates that directly contact the second airstream in the wet passages, thereby evaporatively cooling the plates. The first airstream is cooled by contact with the dry surfaces of the cooled plates, as heat is conducted from the warmer dry side to the evaporatively-cooled wet side. In a typical IDEC design, the first airstream is further cooled, downstream of the indirect stage, in a direct evaporative cooling stage before entering a building as cool supply air.
The predecessor design disclosed in U.S. Pat. No. 5,664,433 to Bourne et al., incorporated herein in its entirety, describes a two-stage evaporative cooler with features that yield a small “footprint”, which facilitates wall mount applications and other installations where vertical space is obtainable but horizontal space is limited. A single air mover is positioned above or beneath the indirect stage, supplying air to the indirect stage in a vertical direction. This predecessor design includes features located in the flow path that split the airstream into one portion that makes two 90° degree turns to travel vertically through the wet passages, and another portion that turns 90° to travel horizontally through the dry passages of the indirect stage and then through the direct stage. The “footprint” can be small in conjunction with tall and narrow indirect and direct stages.